Multistylus facsimile machine



y 1953 F. G. HALLDEN EI'AL 2,639,211

MULTISTYLUS FACSIMILE MACHINE Filed March 25, 1949 ll Sheets-heet 1.

Fl 6. 219 2|a INVENTORS F. G. HALLDEN D.M.ZABRISKIE AT TOR NEY May 19,1953 F. G. HALLDEN ETAL 2,639,211

MULTISTYLU S FACSIMILE MACHINE Filed March 25, 1949 l1 Sheets-Sheet 2 777e 76 I72 97 10 I34 9 I INVENTORS F. s. HALLDEN y D.M.ZABRI SKIEATTORNEY May 19 1953 F. G. HALLDEN ETAL MULTiSTYLUS FACSIMILE MACHINEFiled March 25, 1 949 11 Sheets-Sheet s ATTORNEY May 19, 1953 F. e.HALLDEN ETAL 2,639,211

MULTISTYLUS FACSIMILE MACHINE Filed March 25, 1949 11 Sheets-Sheet 4ATTORNEY May 19, 1953 F. G. HALLDEN 'ETAL MULTISTYLUS FACSIMILE MACHINE'l'l Sheets-Sheet 5 Filed March 25, 1949 INVENTORS F. G. HALLDEND.M.ZABR!SKIE ATTORNEY May '19, 1953 F. G. HALLDEN ETAL MULTISTYLUSFACSIMILE MACHINE 11 Sheets-Sheet 7 Filed March 25, 1949 INVENTORS F G.HA LLDE N E K S R B A Z M D ATTORNEY May 19, 1953 F. G. HALLDEN ETAL2,639,211

MULTISTYLUS FACSIMILE MACHINE Filed March 25, 1949 ll sheets-'sheet 8FIG. I2

00 IIOB lOl INVENTORS F. e. HALLDEN By D.M.ZABRISKIE ATTORNEY May 19,1953 F. G. HALLDEN EI'AL MULTISTYLUIS FACSIMILE MACHINE Filed March 25,1949 ll Sheets-Sheet 9 m m m w AK B a w m m m m F \\k\\ m 4 M 8 2 8 Q Gmu 111i n F m m m P a w u 9 7 m N m a m m F o M F m INVENTORS F. c.HALLDEN D.M.ZABR |SK|E Mm ATTORNEY May 19, 1953 F. G. HALLDEN ETALMULTISTYLUS FACSIMILE MACHINE Filed March 25, 1949 FIG. I9

11 Sheets-Sheet 1O INVENTORS F. G. HALLDEN D.M.ZABRISKIE ATTORNEY y 1953F. G. HALLDEN ET'AL 2,639,211

MULTISTYLUS FACSIMILE mourns:

Filed March 25, 1949 11 Sheets-Sheet 11 INVENTORS F. G.HALLDEN By 0.M.ZABRI$KIE ATTORNEY Patented May 19, 1953 MULTISTYLUS FACSIMILE MACHINEFrederick G. Hallden, Bellerose, N. Y., and Douglas M. Zabriskie,Northvale, N. J., assignors to The Western Union Telegraph Company, NewYork, N. Y., a corporation of New York Application March 25, 1949,Serial No. 83,333

26 Claims. 1

Our invention relates to facsimile machines of the type employing aplurality of stylus elements mounted in spaced relation on an endlessbelt for continuous line-by-linescanning of a synchronously movingsheet. An example of such a machine operating as a recorder is to befound in Erickson Patent No. 2,278,919, issued April 7, 1942.

In those prior multi-stylus recorders it was the conventional practiceto support the paper rigidly along the scanning line by passing itaround a non-yielding cylinder, like a typewriter platen. while thestylus elements were yieldingly mounted on a belt by means of a freelymovable spring arm, which permitted them to move in a direction normalto the paper. The resilient stylus points would thus remain in pressurecontact with the rigidly held paper surface as the belt carried themrapidly across the paper, which was slowly fed lengthwise through themachine as a continuous sheet.

In actual practice this old conventional arrangement of scanning arigidly supported sheet with a train of styluses yieldingly mounted on adriving belt showed intrinsic defects which presented special problemsto overcome them. For instance, with the yieldable styluses it was foundmechanically impractical to maintain absolutely horizontal alignment ofthe stylus points in the operation of the machine so that an accurateeven spacing of the scanning lines was not obtainable. That is to say, astylus point would be apt to travel across the paper in a path that didnot strictly coincide with the path traced by the preceding stylus, withthe result that the scanning lines would be unevenly spaced (or grouped,

as we call it), thus producing a distorted and sometimes unreadablerecording. Also, the yieldable styluses were impractical to maintain astarting alignment of the scanning lines.

When it is considered that in facsimile page recording the transversescanning lines are spaced only 0.01 inch apart, it will be seen thatperfect alignment of the successive stylus points in the scanning pathis anindispensible factor in producing a faithful record. Thedifiiculty. (we might say, the Practical impossibility) of keeping thestylus points in those prior multi-stylus machines in exact alignment asthey moved transversely acrossthe sheet was inherently due to theiryieldable mounting on the driving belt, so that they were free todeviate from their prescribed path of travel.

To overcome this fundamental difliculty and other objections found inprior facsimile recorders of the multi-stylus type, we havedevised anovel machine in which the stylus elements are rigidly held and guidedunder fixed pressure to move unerringly in a predetermined path acrossthe paper which is resiliently supported and bears against the styluspoints under constant tension. Further, our novel stylus support insuresthe starting contact of the successive stylus points on the paper in thesame vertical margin line. This concept of a series of rigidly heldstyluses compelled to travel successively in exactly the same pathacross a moving sheet of resiliently supported paper constitutes a basicfeature of our invention.

Considered more specifically, our new stylus support comprises, in apreferred form, an endless metal band to which several (usually three)stylus holders are rigidly attached at equal distances apart. Eachholder carries a stylus which extends across the band at the requiredtrailing angle. A fixed rail or bar is arranged adjacent to the band insuch position that each stylus, as it moves across the paper, bears withsuflicient pressure against the rail which thus compels each stylus totravel in a predetermined scanning path from which it can not possiblydeviate. We prefer to mount the stylus holders on a band of thin steelwhich is slightly flexible transversely and thereby holds each styluspressed against the rail during a scanning operation, as will beexplained later on.

Since the styluses in our machine are mounted rigidly in a directionnormal to the paper, it is necessary to support the paper resiliently.We accomplish this by providing a movable frame or platen which holds asheet of paper under tension in scanning position so that it constantlypresses against the moving styluses and is free to follow any wear onthe stylus tips. The recording paper is automatically fed in acontinuous sheet from a supply roll and is guided by the platen intoupright position like a flat sheet or page for scanning by thesuccessive styluses. These are so spaced that, as one stylus leaves thepaper, the next one starts its run across the sheet, whereby thestyluses act as a constant load on the resilient sheet for a continuousline-by-line scanmng.

In the operation of the machine as a recorder, a continuous sheet is fedautomatically up the platen at a very low speed by driving connectionsfrom a synchronous motor. The recorded section of the sheet is exposedto view as it moves up and is torn ofi by the operator. Sincetransmitted messages will naturally vary in length, we have provided ahandwheel which enables the operator to measure off the same length ofrecorded sheet to be torn off after a recording operation, no matterwhat the length of the received message. The size of the torn-on sheetwill there fore always be the same.

In a preferred form of our invention the styluses are mounted'in theirholders 6n the steel band in such a way as to be readily replaceable,like a phonograph needle. To enable the operator to insert a new styluscorrectly in its" holder, we have provided a stylus setting gauge on themachine adapted to engage the" tip of the inserted stylus when thelatteris in eiactposition. This gauge assures the c ec't mounting ofevery stylus on the belt" in relation" to surface of the paper to bescanned".

The various novel features and practical ad vantages of our inventionwill be more fully understood from a description of the accompanyingdrawings which illustrate a facsimile recorder constructed in accordancewith our invention and; successfully operated in" a commercial way. Inthese drawings: d

Fig. 1 is a perspective" of our machine with the cover on;

Fig. 1a is an enlarged plan view or a portion of Fi 1;

Fig. 2 is a top'plan view of the machine;-

Fi'g. 3 is a front view of the complete'machine;

Fig. 4.- is a front view of the machine with the stylus drive unitremoved so as to show the paper feed mechanism;

Fig. 5 shows the machine as viewed from the right side;

Fig. 6 illustrates the stylus setting gauge attached to' the machine;

Fig. 7 represents a section on line t i of Fig. 6';

Fig. 8 is an enlarged sectionon line 8--8' of Fig. 5;

Fig. 9 shows a section on line 9 9 or Fig.

Fig. 10 isa section on line 10- -11 of Fig.

Fig. 11 illustrates a left hand side view of the machine;

Figs. 11a, 11b and 110 show the circuits of certain switches mountedonthe machine;

Fig. 12 is a plan view of the stylus carrying band and adjacent parts ofthe paper feed mechanism;

Fig. 13 is a section along line l 3*--l3' of Fig. 12;

Figs. 14 and 15 are sectional views on lines I l--4 and i5i5,respectively, of Fig. 13;

Fig. 16 shows, in greatly exaggerated form, the scanning position of astylus and associated parts;

Fig. 17 is adiagram illustrating the spacing of two consecutivestyluseswith respect to the width of a supported sheet;

Fig. 18 shows a modified form of stylus carrying band; I p

Figs. 18a, 18b and 180 illustrate amodified form of stylus mounting onthe belt Figs. 19, 20 and 21 are enlarged illustrations of the platenstructure, showing the same in plan, front elevation and side view,respectively;

Fig. 22 is a front view of a rnddified form of platen structure;

Figs. 23 and 24 represent enlarged sections on lines 2323 and flit-24,respectively, of Fig. 22; and

Fig. 25 is a transverse section on line 25:25 of Fig. 22.

The apparatus mounted on the base plate l2 of our machine comprises twomain parts or sections: namely, the stylus drive mechanism arranged atthe front as a separable unit and present case" the frame I3 is securedto base I2 in s'uch a" way it is adjustable thereon and removabletherefrom. The right end of plate M reconnected to" base [2 by a screwI! (Fig. 2) which acts as a pivot to permit adjustment of the frame" I3by means of a screw I8 (Figs. 2 and 3). This screw goes into plate Itand has a groovedcollaf 1 9' seated in the open slot 20 or small s 2% isfastened to base 12 by screws 22 By screw it asrequired the en s laswung about the screw If fora-ii adjustment that will he explainedlater. By" simply removing the screw I?" the frame t3? and themechanismcarried thereby can be lifd off the base |;2=- as" a unit theslotted lug 21' permitting the withdrawal o'fadjustin screw t8.

Re ferii'nLg" to Figs. 2 5 and a yoke-sha ed bracket 2'3 is secured to'from. race or the upright plate l5 by screws 2'4. The bracket 23extends" forward and terminates a bearing 25 which isin transversealignment with a}- rear bea'ring ill? on the" bracket td= support arotary shaft 21. "rue plat-e I S-ischt away at 2-8 to make room for therear beaii h ig 26.- At friction" drive clutch, indicated as a unit by"K is mounted on shaft 21 to connect the latter with-asynchronous motor2a which rests: onthe base plate- M and is suit ably secured in place. i

As die-any shown Figs. 9 and 10', the friction clutch has a; hub 30which is keyed to the shaft by a} pin 3|. The reduced forward endof hub30 carries a' friction sleeve 32. or felt or the like, on which threesegmental blocks 33 are mounted with a slight clearance between them.These blocks, which" may be of hard insuiratin'g material", are formedwith a peripheral groove 34 in which a circular coil spring 35 isseated. This s ring, by its constant tendency to contract, exerts aradial pressure onthe blocks 33 which are thereby held infrictionaldriving com tact with the hub 3'0 through the clutch sleeve32.

Av worm gear 36-, preferably but not necessarily of insulating"material, is rotatably mounted on shaft 2'! and is c'ioupled to thesegmental blocks 33 by means of a metal disk 31 whichis secured to therear face of the gear by screws 38''. The disk 31 has three equallyspaced notches 39 which fit over corresponding lugs- 4-t' projectingforward from each of the clutch blocks 93. Only oneinterlockingconiictidn 39'40 is shown in Figs. 9' and 10, but it will beunderstood that there are three such connections betweenthe parts 3'0and 31 arranged apart. The gear 3t is held against forward axialdispl-ace'inent on shaft 2'? in any practical way, as by a thrust washer4i and a snap rifig' 42'.

The worm gear 36 is permanently in mesh with a worm pinion d3 fixedm-the motor shaft 44 so that the shaftjl is driven through thefrictional clutch K when the shaft is' free to rotate.

In that case the gear 36' and hub 39 operate as a unitary drivingconnection between the motor 29 and the shaft 21. However, when thisshaft is locked against rotation (as we shall presently describe) whilethe motor 29 is running, the gear 36 and clutch blocks 33 rotate asbefore, but now these spring pressed blocks slip over the stationary hub30 as permitted by the friction sleeve 32.

Still referring to Fig. 9, a stop disk 45 is fixed on the front end ofshaft 21 by a collar 46 which is attached to the face of the disk byscrews 41. A radial set screw 48 in collar 46 enters a groove 48 inshaft 21 and locks the disk 45 to the shaft. Turning now to Fig. 3, itwill be seen that the disk 45 has a peripheral tooth or stop 49 arrangedin operative relation to an electromagnet 59 which is fastened to thebase flange 16 by screws passing through the L-shaped frame 52 of themagnet assembly. An armature bar 53 is pivoted at 54 to the magneticframe 52 and is normally held in raised position by a spring 55. Whenthe armature 53 is raised, it interlocks with the tooth 49 on disk 45,whereby the shaft 21 is held locked against rotation as long as themagnet 50 remains inert. When this magnet is energized, the armature 53is pulled down to release the disk 45 and the clutch shaft 21 is free torotate in a clockwise direction (as viewed in Fig. 3). The disk 45cooperates with a thrust washer 56 back of bearing 26 to hold the shaft21 against axial displacement.

The magnet 50 also controls a switch 51 which is suitably attached'to atransverse web 58 of the L-shaped casting 13 (Fig. 3). The switch 51 hasan arm 59 (Fig. 9) arranged to be operated by the armature 53 when themagnet 59 is energized. The purpose of switch 51 is to control thepositive and negative potentials on certain phasing lines going to thedistant transmitter of the system in which our recorder is connected.The phasing circuits controlled by switch 51 are not a part of thisinvention and are therefore not shown in the drawings. However, we haveindicated the contacts of switch 51 diagrammatically in Fig. 111) toshow what happens when the switch arm 59 is operated by the energizedmagnet 50.

Inside the switch box 51 are three contacts 60, 6| and 62. connectedmechanically to the arm 59 and is thereby normally pushed out (that is,upward as in Fig. 9 and to the right as in Fig. 11b). The two outercontacts BI and 62 are permanently connected to a local battery with theplus tery z.

.the local battery keeps a positive potential on line 63. When themagnet 58 is energized from the transmitter (at the phasing moment ofthe machine), the armature 53 not only releases the disk 45 and theclutch shaft 21 but also operates the switch arm 59 to close the contact62, whereby positive potential is removed from line 53 and negativepotential imposed thereon. It is un- The middle contact 60 is a springnecessary to describe what this change of potential does at thetransmitter because that operation does not belong to the presentinvention. For convenience we shall designate magnet 58 as the phasingmagnet.

Referring particularly to Figs. 9 and 13, the rear end of clutch shaft21 extends beyond the vertical plate 15 and carries a driving pulleywhich comprises a metal wheel 61 fixed over a hub 68 of hard insulatingmaterial (like linen Bakelite). The hub 68 has a flange 69 through whichscrews 10 pass into the metal wheel 61 to secure those two partstogether as a unit. It will be convenient to refer to the assembly 6158as the driving pulley 61, which is connected to shaft 21 in anypractical way, as by a set screw 1| inserted through a radial hole 12 inthe pulley. The set screw 11 is clear of the metal body of pulley 61,which is completely insulated from shaft 21 and the grounded frame ofthe machine. The pulley 61 carries four pins 13 which are evenly spacedand extend axially rearward for a purpose to be described later.

Referring to Figs. 2 and 3, there is shown at the left side of themachine a bracket 14 secured to the upright plate l5 by screws 15 andhaving a hub 16 which projects rearward through an opening 17 in theplate. The screws 15 pass through slots 15 in bracket 14, whereby thelatter is adjustable toward and away fromthe pulley 61. A stud 18supported in hub 16 extends rearward and has an idler pulley 19journalled thereon. As best shown in Figs. 13 and 14, the pulley 19 hasa central bushing 88 of insulating material so that the metal body ofthe pulley is completely insulated. A lock nut 81 retains the idlerpulley .19 on the stud 18.

As seen in Fig. 13, the two insulated metal pulleys 6'! and 19 are ofthe same size and are arranged in alignment to support an endless metalband or belt 82 which is preferably a thin flexible strip of bluetempered spring steel. The pulleys 61 and 19 are each provided with aplurality of radial pins 83 (in this instance four) spaced equally apartand projecting through a peripheral groove or channel 84 formed in themetal rim of each pulley. The belt 82 has accurately spaced holes 85(Fig. 12) for receiving the tips of the pins 83, whereby the bandisconnected to the pulleys in a positive drive free of slippage. Thesprocket pins 83 also prevent the belt from weaving (that is, shiftinglaterally) on the pulleys. This is the sole function of pins 83 on theidler pulley 19.

The belt 82 is wider than the pulleys 61 and 19 so as to projectrearward beyond the pulleys (Figs. 8 and 14), for a purpose that willbecome clear in due course. The ends of belt 32 are riveted together asshown in the enlarged view of Fig. 8. One end of the belt is taperedoff, as shown at 86 (Fig. 5) while the other end 86' is straight. Itwill be seen that the tapered end 86 extends into the pulley channel 84where the two ends of the pulley overlap, with the tapered endunderneath. The overlapped ends of belt 82 are secured together by abond comprising a pair of washers 8188 and a rivet 89. The pulleychannels 84 accommodate this riveted bond in such a way that it'does notinterfere with the smooth riding of the belt over the pulley rims, aswill be clear from Fig. 8. Since the belt travels from left to right(moving downward over the driving 'pulley in Fig. 5), we shall refer tothe tapered end 86 as the trailing end of the belt. The adjustment ofidle pulley 19 ;by means of of prime importance.

7 the slots '75 "makes it easy to 'fit th endless belt taut around thepulleys and to remove the belt when necessary.

The function of belt 82 is to carry a plurality of styluses 90successively across a sheet of paper in a prescribed linear path. In oneform of our invention such stylus is rigidly mounted on the belt 82 asillustrated in the enlarged view of Fig. 16. A small block or plate 9|is fastened to the outer side of the belt by screws 92 or otherwise, andon top of this plate is mounted a stylus holder 93 which is shown in thepresent embodiment as a small metal tube with a flat bottom so that itcan be securely soldered in place.

Each holder 93 is provided with a bore or channel 93' adapted to receivea stylus 9B which is removably clamped in position by a thumb screw 94.It will be seen that the parts 9| and 93 constitute a unitary stylusmounting rigidly secured to the band 82. In other words, the stylus 90is a rigid part of the belt, and this feature is The holder 53 and thethumb screw 94 make it easy to insert and remove a stylus. As seen inFigs. 12 and 18, the holder 93 is fixed at an angle transversely of thebelt 82 so that the stylus so can engage the paper in a trailingposition for scanning. The practical importance of mounting each stylus9i) rigidly (as opposed to resiliently) on the metal band 52 will becomeapparent as the specification proceeds.

We direct attention here to the novel construction of the stylus element90 (Fig. 16). At the present time we make this part from a single rod ofhard drawn tungsten formed with a conical or tapering shoulder 95 and ascanning point or tip 96 which'is like a short piece of stiff wire. Thecylindrical body portion of the stylus fits into the holder 93 andextends out of it a certain distance. The purpose of this extension andthe function of the tapering shoulder 95 can best be explained later inconnection with other mechanism of the machine. The scanning tip at,instead of being an integral part of the stylus element, can also be inthe form of a separate wire inserted into the end of the stylus body.

We shall now describe our novel guide mechanism associated with theupper run of the belt or band 82 for completing the stylu-ses 9D totraverse the same linear scanning path without the possibility ofdeviation. This stylus guide is one of the important features of ourmachine.

lteferring particularly to Figs. 2, i3, 15 and 16,

it will be seen that the upright plate I carries two insulating blocks53'! which are attached to the rear face of the plate by screws or bolts95. On top of the blocks 91 is mounted a heavy channel bar 99 which isfastened down by bolts I00 passing through the blocks. The channel bar99. which isv of good conducting metal (such as brass), is mountedbeneath the upper run or stretch of the stylus belt I32 in alignmenttherewith, so that the belt rides along the top edges of the bar, asclear from Figs. and 16. One of the bolts 99 acts as a binding post forconductor IIlI for connecting the insulated styluses 90 in circuit.

The guide bar 99 has a pair of metal strips I02 and I93 secured to'thesides thereof by screws I04 and I05, respectively. As best shown in Fig.16, the strips I-li2--II)3 have turned in flanges I06 and I01 which areslightly spaced from the channel bar 99 to form lateralgrooves I01 forreceiving the sides of belt 82. The grooves or channels I01 guide andhold the upper run of the belt'in a fixed path. Let it be noted at thispoint that the tapered trailing end '86 of belt 82 insures an easyentrance of the belt into the guide channels I01 and a smooth passagetherethrough. Because the upper or scanning run of the belt is supportedin the narrow side channels I01 and is furthermore held against weavingby the sprocket pins 83, the tightness or sl'ackness of the returningpart of the belt is not critical and no tensioning device is needed.This adds to the simplicity of the machine and reduces its productioncost.

A rail I08 is fastened to the rear strip I03 by rivets IIlBa orotherwise. Holes Will) in rail I08 allow it to clear the screws I05, sothat it lies flat against the strip I03 (Fig. 12). The rail I08, whichis a rigid bar of hard wear-resisting metal, extends above the strip I03and is in the path of the moving styluses 90. That is, the top of railI06 is a little higher than the normal position of the styluses on thebelt 82. The ends of rail I08 are beveled at I08 (Fig. 13) so as toguide the styluses onto and down from the rail by an easy movement.

The stylus guide assembly as above described operates as follows: As astylus Sb rides over the beveled front end I88 of rail I98, it is forcedslightly upwardly against the tension of the spring steel band 82. Asshown in the exaggerated view 01 Fig. 16, the upward deflection of thestylus as it rides onto the top of rail I88 causes a slight transversedistortion of the steel band 82, which thereby exerts a downward pull onthe stylus and holds it firmly in pressure contact with the straight topedge of rail Iilll. This uniform pressure engagement of each stylus ill)with the fixed guide rail H38 assures perfect alignment of the styluspoints in a horizontal direction so that they trace successively theidentical scanning path with absolute fidelity. Consequently, the styluspoints produce evenly spaced scanning lines which give a clear copy ofthe recorded message. Because the rail I98 prevents uneven spacing orgrouping of the lines, we call it the anti-grouping bar of the machine.We use the convenient term rail as applied to the part I08, both in thedescription and claims, to represent broadly any form or kind of rigidbar or like member which provides an unyielding guide track for thestylus.

If it should be desirable in some cases to in crease the transverseflexibility of the steel band 82 at the points where the Styluses aremounted. that can be done, for instance, by cutting away an arc-shapedportion 82' along the edge of the belt (Fig. 18). It may be noted herethat the adjustable mounting of idler pulley is by means of the slots 55permits removal and replacement of the belt without disturbing theadjustments of the guide strips Hit-Hi3. and theguide rail IIBB.

A modified form of rigid stylus mounting is shown in Figs. Illa-18c,where the stylus holder 93, instead of being attached directly to thebelt 82, is mounted on the free end of a stiff spring plate )9 which isriveted to the belt at $2 and extends lengthwise thereof. A metal block91' is mounted on the spring plate I (I9 and the stylus holder 93 issoldered to the block. The spring plate I09, which is simply a flexuralpart of the belt structure, lies normally flat on the belt, as shown inFig. 18a. As the stylus rides over the curved front end ms of the guiderail I08, the plate I09 is flexed upward (Fig. 13b) and exerts aconstant downward pressure on the stylus, which is thereby held in firmcontact with the to of rail I88. The effect thus produced is preciselythe same as that of the transversely flexed belt 82 in Fig. 16, the onlydifference being that in Fig. 16 the lateral distortion of the belttilts the stylus 90 slightly upward, whereas the plate I09 holds thestylus practically horizontal, since the belt remains flat.

It will be apparent, then,'that the function of the transverse flexureof belt 82 in the embodiment shown in Fig. 16 is taken over by the stiffspring plate I99 in Figs. 18a-l8c. In other words,

these rigid stylus mountings utilize a fiexural part of belt 82 toenable the styluses to ride up onto the guide rail I08 and remain inpressure contact therewith during a scanning operation. Let it be notedthat as each stylus 99 (in either form of mounting) rides over the railI99, it is held rigidly not only in its horizontal line of travel butalso in a direction atright angles thereto. In the actual machine,the'upward movement of a stylus on the belt from normal to scanningposition is only a few thousandths of an inch.

Before leaving the belt drive mechanism mounted on the removable frameI3, we would call attention to a few additional details. The motor 29 isof the split-phase synchronous type and accordingly requires a startingcondenser, which is shown at III) in Figs. 2 and 3. This condenser isattached to the upright wall I by screws IIII'. A handwheel I I2 on theleft end of the motor shaft enables the attendant to turn the stylusbelt 82 when the machine is not running, as when it is necessary toinsert a new stylus in a manner to be described later.

Referring to Figs. 2 and 3, it will be seen that at the left side of themachine, next to the motor star-ting condenser III], is a multi-contactplug I'I3which is fastened to the wall I5 by screws H4. The plug H3 isadapted to receive a socket H5 (Fig. 11) connected to the front end of acable H9, which goes to the rear of the machine and contains certainwires for operatively connecting the recorder in the system in which itis used. The practical advantage of the separable electrical connectionII4-I I5 lies in the fact that it makes the belt drive units of ourmachines easily removable and interchangeable. For instance, if the beltdrive mechanism of a certain machine requires repair, it is onlynecessary to loosen the screw N (Fig. 2), pull out the socket II5,remove the mechanism and insert a new one, so that the machine will notstay out of commission.

The paper feed mechanism A second main assembly of our machine is themechanism back of the stylus drive unit for supporting and feeding acontinuous sheet of paper in operative relation to the styluses 90 onbelt 82. We shall now describe the details of this mechanism asillustrated in the drawings.

The main base I2 of the machine supports a pair of upright side platesH1 and H8, arranged crosswiseof the machine (Fig. 4.). These side platesare secured at the bottom by screws H9 to a bedplate I20, which isattached to the base I2 by screws I2I. (Fig. 9). right plates II'I-II8are connected by a cross piece I22, which is fastened down by screws I23(Fig. 2). The connected parts II'I-I I8--I2Il I22 constitute the mainsupporting framework of the paper feed mechanism.

The right-hand side plate I I1 carrie a straight bracket I24 and theother plate II8 supports an angular bracket I25, these brackets beingsecured At the top the up-' 10" by screws I26 or otherwise (Figs. 2, 5and 11). The brackets I24 and I25 extend rearward to support the coreI2I of a paper supply roll I28 which is wound on a pasteboard tube orspool I28. The core I2I, which may be of hard Wood, is provided at theright end (Fig. 2) with an annular flange or shoulder I29, and the leftend of the core has a circular groove I39 in which a looped coiledspring I3I (usually called a spring garter) is seated. The spring I3Icooperates with the shoulder I29 to retain the paper roll I23 on thecore I2'I.

The left end of core I2'I has a tapered portion I32 and a shoulder I32.A suitable brake band I33 passes over the tapered end I32 and is heldunder constant tension by a contractile spring I33a (Fig. 11). The frontend of brake band I33 is fastened to a pin I331) projecting from theside plate I I 8, and the lower end of spring i33a is at-' tached to ahook I33c, which is secured to a bracket I33d on base plate If. Thetensioned brake band I33 places a constant load on the core In toprevent the paper from being wound off too fast, especially when thesupply roll is getting low and there is little weight on the trunnionsof the core.

Referring to Figs. 2 and 9, as the paper unwinds from the supply rollI23, it passes down-- ward as a continuous sheet I34 around an idlerroll I35, which is pivoted on trunnions I36 ad. justably supported onsuitable brackets I3'I mounted on base plate I2. From the idler or guideroll I35 the sheet I34 passes through a horizontal chute I38 formed by apair of thin metal plates I39 and I40 which are slightly spaced apart.These two plates may be separate pieces soldered together or they can bea single piece of sheet metal (such as brass) lapped over to provide theshallow space or chute I39. The plate I39 is secured to the cross piecei229 by one or more screws I39 which are sunk so as not to obstruct thechannel I38. At the rear, the lower plate I39 has a slanting section I4Ito guide the end of sheet I34 into the chute I38 when a new roll ofpaper is inserted. At the front the plate I39 passes around a feedroller I42, then upward to form a stationary apron I43 in front of thesheet I34.

The feed roller I42 is preferably covered with rubber to form a goodgripping surface for the paper sheet which passes between the roller anda pair of pressure wheels I44 mounted on a shaft I45 (Figs. 4 and 9).The ends of this shaft rest in slotted brackets I46 (Figs. 5 and 11)secured to the side plates I I1 and I I8. Contractile springs I41attached to the ends of shaft I35 hold the wheels I44 continuouslypressed against the feed roller I42 toinsure proper feeding of the paperwhen the roller is operated. The springs I41 allow, the shaft order tohold the wheels I44 temporarily away from the roller I42, as indicatedat 144 in Fig. 11. This makes it easier to insert a sheet around thefeed roller I42 which is mounted on a rotary shaft I 48 journaled in theside plates Ill and H8. The left, end of shaft I48 carries a gear I49arranged in permanent mesh with pinion I59 on the driving shaft I5I of asmall synchronous I45 to be pulled forward by hand against the frontedge of brackets I46 in invention. The construction of this platen, in-.dicated as a whole by P, is shown by itself in Figs. 19, 20 and 21 inenlarged proportions for clearness, and its mounting in the machineappears in Figs. 4, 5, 9 and 11.

The platen P is a rectangular frame comprising a sheet metal plate I53provided with a pair of side wings I 5.4 which are doubled over to. formtwo narrow channels I55 adapted to receive the sides of the paper sheetI34 (Fig. 4). The lower corners I54 of the wings. I54 are preferablybent forward to guide the inserted sheet into the channels I55. Theplate I53 carries near the bottom a pair of right angled side pieces I56adapted to receive trunnion screws It? (Big. which are supported on thebrackets I46 and enter holes I57 in members I56 (Fig. 21). The screwsI51 are adjustable to centralize the platen. It is clear, then, that theplaten P is hinged at the bottom to rock about the pivot axis I57.

The upper edge of the plate I53 is folded over at the ends to provideslotted extensions I58 which are connected by a strip I59. Theextensions I58 and strip I52)v form a thin transverse slit I59" adaptedto receive and guide the paper sheet I34. The outer ends of the slottedexten sion's I58 are curved rearward so as to bend the sheet I34 back atits side edges, as indicated at I60 and IGI in the diagrammaticillustration of Fig. 17. The purpose of the lateral flexures I'Gll-I-SIon the supported sheet Itt will appear later on.

A channel bar I62 is secured to the top edge of plate I53 and extendsbeyond the same to provide a recess or chamber I63 (Fig. 16) behind thesheet I3d along the scanning path of the Styluses 90.. The bar I62 is ineffect a grooved or channeled extension of plate I58 and could be madeintegral therewith. Although the sheet supported by the platen lies flatagainst the plate I53, the stylus points 55 press against a yield-ablesection of the sheet due to the recess I63. Another funetion of thisrecess is to permit free travel of the stylus band 82. without damage tothe stylus points when there happens to be no paper in. the platen. Inthat case the stylus tips would ride through the uncovered recess I63.

The platen P is maintained in a resilient position by a contractilespring I64 (Fig. 9-) which isv attached at its upper end to a stud I65depending from the top bar I22, and the lower end of the spring isconnected to a bracket arm I 66 extending from the plate I53. It isclear from Fig. 9 that the constant upward pull of spring I64 on thepivoted platen holds the latter tilted forward in a resilient position.That is to say, the platen P always tends to rock forward about itsbottom pivot I51, so that the resiliently supported paper sheet bearsunder constant tension against the rigidly mounted Styluses 90 as thelatter move across the sheet.

It is desirable to keep a constant frictional load on the resilientlysupported platen P to reduce the vibration caused by the impact of thes-tyiuses 90 on the paper when they first make contact with it. In thepresent machine (Fig. 9) we attach a spring blade I'Iii to the top ofthe channel bar I62 and this blade extends rearward between a fixed pinI62; and an adjustable cam Hi9 mounted on the :side plate I I8 by aspring I769- By rotatably adjustingthe cam I59, the spring blade IE7 isplaced under more or less tens'ion to exert the proper amount offriction on the movements of the platen frame. In other words, thefriction blade I6 7 acts like a s'n-ubber 12 to damp the vibrations ofthe pivoted platen under the rapid tapping action of the styluses 90 as.they strike the paper in quick succession.

As seen in Fig. 9, the sheet I34 passes upward from the platen P througha slot I7II formed by a pair of spaced parallel bars "I and I72 whichare attached to the side plates H7 and H8 by screws I73. Mounting blocksI74 and I75 support the bars "I and I72 in properly spaced rela tion tothe platen. The front bar I7I, which we preferably make of a hardtransparent material such as Lucite, has a sharp edge I7I to act as aknife for cutting off the section of paper that projects out of themachine. The transparency of the knife bar I7l enables the operator tosee when the last line of a recorded message has gone past the knife sothat he can make sure of cutting off the complete message. Y

The paper feed roller I42, which is driven by the synchronous motor I52during a recording operation, is also operable independently of themotor by means of a. handwheel I76 arranged for easy access at the topof the machine. Although only one wheel is needed, we prefer to use a.pair of them for convenient manipulation from; either side of themachine. The hand whee-ls I76. are fixed on the ends of a shaft I77(Figs. 2 and 9) which is journalled in the side plates II7----III3 andprojects beyond the same. The right end, of shaft I77 carries a sprocketI78 which is connected by a drive chain I79 to a sprocket I80 on the endof the feed roller shaft I 48 (Figs. 4 and 5).

The, wheels I75 are preferably knurled on the periphery so that theoperator can easily turn them with his fingertip or palm bymerelypushing them rearward at the top, as indicated by arrows Itl inFigs. 1, 5 and 11. This manual operation of wheels I76, which occursonly when the machine is not manning, turns. the roller I42 to feed thepaper upward on the platen for purposes to be presently explained. Itgoes without sayingthat. the gear connections between the feed rollerI42 and the driving motor I52 are such as to allow the manual operationof wheels I76 when the motor is deenergiZed. Of course, whenthe feedroller is operated by the motor I52 during a recording cycle, thehandwheels I78 turn with it through the sprocket chain I79.

Referring to Fig. 1-1, on theleft end of shaft I 77 is fixed a cam diskI82 which has. a tooth or pro,- jec-tion I83 arranged to operate aswitch arm I84. For brevity, we shall refer to. the part I83 as the cam.The arm or lever I84 belongs to a switch I35 of standard construction,such as a microswitch, requiring no illustration or description. It isenough to say that the switch I85 is normally closed and is opened whenthe cam I83 moves the pivoted arm I84 down (as viewed in Fig. 11). Whenthe cam I83 disengage's the arm I841 the latter is automatically pushedout by a suitable spring action within the switch box to close theswitch contacts I 86, as indicated diagrammatically in Fig. lie.

The switch I85 is in the-circuit of a signal lamp- I87, which is put outwhen the cam I83 strikes the arm I84. Although the signal lamp I87 isnot a structural part of our machine, it is functionally connectedtherewith and is mountedwithin sight of the operator. The purpose oflamp I87 can be told better when we describe the. operation of themachine.

The handwheel I76 Iforconvenience ofdescription we shall consider thetwo wheels as one) is.

provided on its periphery with a mark I88. which may be of any suitableform or character so as-to be easily seen by the operator. In thepresent machine as actually built, the mark I88 is a small plug ofcolored bakelite pressed into a slot of the wheel, and we usually referto this mark as a bead. There is a definite angular relation between thecam I83 and the mark I88, as shown in Fig. 11. When the mark I88 on thehandwheel I16 is near the top where it is easily seen, the cam I83 isjust in front of the switch arm I84, which therefore remains in closedposition for almost a full revolution of the wheel in the direction ofarrow I8I.

When the indicator mark or bead I88 is at I88, the cam I83 is at I83 andactuates the arm I84 to open the switch contacts I86 and extinguish thesignal lamp I81. As the wheel completes its turn, the cam moves past theswitch arm I84, which instantly returns to normal or closing position,as illustrated in Fig. 110. At this moment the bead I88 is back in startposition on top of the Wheel I16, as shown in Fig. 11. A suitableindicator I89 (Figs. 1 and 1a) is placed on the cover I98 of themachine, so the operator can see when the wheel I16 has completed itsturn and stop it in that precise position.

The chief function of handwheel I16 is to enable the operator to measurethe exact length of sheet to be torn off by the knife I1I after eachrecording operation. The driving connections between the wheel I16 andthe feed roller I42 are such that every revolution of the wheel feedsout a telegram-size sheet above the cutting edge of knife Hi. If thewheel I16 stops short of a complete turn after a recording operation (aswhen a short message has been transmitted), the attendant turns thewheel rearward by hand until the bead I88 registers with the fixedindicator I 89. Then the projected sheet bearing the recorded message istorn off along the edge "I. In our present practice, the length of atelegram sheet is 5% inches and the width of the sheet (which is thewidth of the paper roll I28) i 8% inches. These figures are mentionedmerely by way of example.

Operation of the machine We are now prepared to follow the operation ofthe machine in recording a transmitted message. It should, of course, beassumed that the receiver is in operative communication with a distanttransmitter through a cable I88 (Fi 2), which is electrically connectedto the recorder circuits by a separable plug-and-socket unit I9I mountedin the back of the machine. Let us further assume that the recordingpaper is in the platen P with the top of the sheet torn off along theknife I1I. The handwheel I16 is in starting position with the bead I88opposite the indicator I89. The stylus driving motor 29 is running, butthe stylus belt 82 is not moving because the clutch shaft 21 is heldlocked by the unenergized magnet 50.

The moment that the magnet 58 is energized by a phasing pulse from thetransmitter, the shaft 21 is operated through the friction clutch K andthe pulley 61 drives the belt 82 at predetermined high speed. At thesame time, the synchronous motor I52 is energized and operates theroller I42 to feed the paper upward in the platen at a very low speed.As the styluses 88 travel rapidly from left to right across the slowlyrising sheet, each stylus traces a line and makes a mark on the paperevery time a signal impulse is received. This method of facsimilerecording on electrosensitive paper is so well known to engineers as torequire no description here.

As previously pointed out, each stylus is held rigidly in identicalscanning position as it travels across the sheet inpressure contact withthe guide rail I88, which prevents vertical displacement of thestyluses. At the same time, the metal band 82 holds the styluses 98against horizontal or lateral derangement with respect to the scannedsurface of the resiliently supported sheet I34, which bears against thestylus points under fixed tension. As a result, the successive linesmade by the styluses on the slowly moving sheet are spaced with perfectevenness and produce a correspondingly clear facsimile record. I

In commercial practice, we use one hundred scanning lines per inch,which have been found to give the most satisfactory results.Accordingly, the paper moves at the slow rate of 1.80 inches per minute,while during that same interval the three styluses make 180 scanninglines. In other words, the belt 82 travels at such speed (180 R. P. M.)that it takes each stylus only one-third of a second to travel acrossthe sheet. This gives an idea of the speed at which our machine records.Of course, these figures serve merely as a practical example and are notto be considered in any restrictive sense. I

It is important to note the spacing of the styluses from each other asindicated in the diagram of Fig 17. As one stylus is leaving the flatsection of sheet I34 at the right, the next stylus is entering at theleft and takes up the load of the resiliently mounted sheet which isconstantly pressing against the stylus points under the action of theplaten spring I64. It is thus clear that during a recording operationthe sheet on the platen is engaged without interruption by thesuccessive styluses. In other words, the forwardly urged platen P alwaysfinds a rigid stylus in position to bear against.

It will be noted that the rearwardly curved front edge of the sheet onthe platen (see Figs. 17 and 23) allows a gradual easy entry of the fastmoving stylus points onto the sheet, so that no injury is done to thepaper. While only the entry edge I60 of the paper (in this case the leftone) need be flexed back, we have shown both edges in that position.

As previously explained, the stylus drive mechanism is adjustable toswing the left or leading end toward the platen so that the styluspoints approach the curved left edge I88 of the sheet at an angle. Thisangular approach permits the stylus points to enter upon the paper sogradually that the paper is not torn when the belt drive mechanism isadjusted by the screw I8 while the belt is running,

In the particular machine shown in the drawings, the distance betweenthe axis centers of the belt pulleys 61 and 18 equals the width of thefiat section I34 of sheet I34, as indicated in Fig. l? by the horizontaldistance between the two imaginary lines I34a and I341). However, thisspacing of the pulleys, While adding to the com.- pactness of themachine in some designs, is not essential, and the pulleys can bearranged farther apart, as they would be, for instance, when the stylusmounting plate I89 (Figs. l8a-18c) is used. What is important is theexact placing of the rigid stylus mountings on the belt so that thestylus points shall contact the paper along the imaginary marginal lineI34a on the leftand leave the paper at the right marginal line I341).

.As, shown in Fig, 9, the platen P tips forward at the top so thatthe'flat section of paper supported by'the platen inclines rearwardly atthe bottom. Therefore, while the paper is held against the scanningstyluses at the top, the lower portion of the paper is held away fromthe inactive styluses in the lower run of belt 82. In this way thereturning styluses are kept from striking and injuring the paper.

Let us remember that during a recording op eration the handwheel Il'titurns from its starting position in the direction of arrow I8! (Fig, 11)and its final position will depend on the length of the recordedmessage. That is to say, when the handwheel stops at the close of arecording operation, the indicator bead I88 on the wheel will besomewhere less than a full turn from its starting point. We are toassume that at the close of a recording cycle the paper feed motor IE2is automatically deenergized, thus stopping the wheel I76. At the sametime the magnet 5E3 is released to lock the clutch shaft 271 (Fig. 3band stop the belt 32, Aside from the stopping of the recordingmechanism, the completion of the recorded message is signaled to theoperator by the lighting of lamp 18's through suitable control circuitswhich do not belong to this case and therefore require no description.

We have, then, this condition at the close of a recording operation: Theend-of-message lamp I8? is lighted, a portion of the recorded section ofthe sheet is projecting out of the machine, and the handwheel H6 "isstopped after making less than one full turn. The operator now turns thewheel I'I'fi rearward by hand until the bead I88 is opposite theindicator use (Figs. 1 and 1a). The full length of {the recorded sheetisnow projected past the knife Ill and the operator tears off thefacsimile telegram sheet for delivery to its destination.

Shortly'before the head I88 comes in line with the indicator ["69 as theoperator turns the wheel lit to measure oii the recorded sheet, the lampI8? goesout. In Fig. 11 this happens when the bead I88 is in positionI88, for then the cam 83 operates the switch arm M to "break thecontacts I6 and open the "lamp circuit. The extinguishing of lamp I81serves as a supervisory signal which lets, the operator know'that itii'ssafe to disconnect the receiver from the transmitter.

When the facsimile recording is done by an electric stylus onelectrosensitive paper, a kind of soot collects on the stylus point as aproduct of combustion resulting from the action of the stylus on'thepaper. Unless this soothe removed, it will be carried along by'thestylus and smudge the recording. To prevent this, we provideautomaticmeans for cleaning each stylus before it moves into contact with thepaper. Referring to Figs. 2 and 5, a-circular brush I82 is mounted on abracket I93 by means o'f astud 194 on which the brush can turn. Thebracket I9 3 is attached to the left end of plate [5 and projects towardthe rear. A-finger piece i9 2 allows axialadjustment of the brush I82 to-locate it properly-in the-path' of :the-styluses 90. I

As each stylus moves upward-on theleft-pulley I9, it encounters thebrush I92 which-knocks off any soot that may have gathered on the styluspoint. And right here lies the practical advantageof the slopingshoulder 85 provided on each stylus. With a square shoulder on :thestylus, the soot would stick in-the corner'and accumulate in a pilewhich wouldbe difiicult to remove. However, by making'the shoulder tficonical we e1imihate all corners so that no soot :can pile up. Whateverparticles "of soot cling to the sloping surface 95 are easily flickedoff "by the bristles 16 of brush I 92, which is turned a little by eachstylus and thus presents a fresh cleanin surface to the next stylus. Asa result, we always get clean clear copy. Further, by thus utilizing allthe bristles we increase the life of the brush.

The stylus setting gauge As can be readily seen, it is essential thatthe stylus tips 96 terminate in the same vertical plane. We obtain thiscritical adjustment of the Styluses on the belt 32 by means of a gaugeI55 mounted on the outer face of the right-hand plate H7, as shown inFigs. 5, 6 and "7. The stylus gauge I 95 is a metal plate having anopening 2% and two slots I91 and I98. TWO Pills I99 and 2M carried bythe upright plate IITI project laterally through the slots l9! and 1 98,respectivcly, whereby the gau e I95 is .slidably supported on plate Ill.The pin I99 has a head Ills ,for retaining the gauge I95 on its supportand this head (Fig. 7) is slightly spaced from the gauge to allow alateral movement thereof for a purpose that will presently appear.

The supporting plate III has a slot 20-! in which is nod a catch ordetent .262, shown here as a circular head on a screw .203 by which thecatch m2 is adjustable along the slot 204. The opening M6 in gauge 2:85is shaped to provide :a straight shoulder 2st adapted to engagethe-catch A contractile spring 205,, attached to the gauge I at 72% andto the plate l lg! at 201 always tends to pull the gauge rearward andthus holds the shoulder 2E4 pressed against the detent m2. This looksthe gauge plate Jfidand places the vertical front edge 2-018 thereof apredetermined position .to set the stylus points.

Assuming that the gaug N55 has been properly adjusted for thisparticular machine in relation to the belt 82, the operator proceeds :as-,,follows .to inserta-new stylus: By turning the hand=kn0b M2 (Figs.Zand .39, he=moves1thebelt :82 until the stylus holder 593 which is toreceive a new stylus is in line with the edge 2.8.8 of the gauge (Figs.6 and 7). When the stylus 9c is inserted in the holder, it is movedtoward the gauge until the tip of the stylus touches the edseZllB,Whereuponthescrew 9t tightened to clamp the stylus in its set position.This simple procedure insures the positioning of the stylus tips in thesame vertical plane on the'belt.

"The gauge I has a front extension .20.;9 larranged in the path of thelateralpins 1-3 .on the driving pulley El. Therefore, the-first .pinthat strikes the extension 23% moves .the gauge J85 sideways (amovementpermitted by the retaining head we" and releases Ltheshoulder20.4 from the "catch 252. The spring 2.05 instantly pulls the releasedgauge rearward, ,as shown .in-Fig. @5, so that the tips of the .stylusesso l-wiulnot encounter the gauge. To set the gauge .-forward again, theoperator grips it by the handle .210 (which may be an integral.lateraLfiange) and pulls it forward to .theflpositionshown inJFigQG,until the shoulder 2M automatically ,sn-aps rinto locking engagementwith the -.catch".'2 02.

n is advisable tolet the attendahtgknowmhen the paper supply is runninlow, and forthat purpose We provide an automaticlsignal operated by apivotedzarm orlever 2H under controLof the paperroll 12s (Figs. 5 and.9) The .armQ'ZH isSuitably pivoted at 12 on the .bracket lead and itsfree endhasla muerzw in contactwith the paper roll at the bottom. .Theothenen d of arm 2 H [is connected to .alcontr-actile spring 2 Iii whichconstantly pushes .the roller t2l 3 against in place.

to the paper.

the paper, so that the roller automatically follows the paper as theroll gets smaller.

The arm 2II operates a suitable switch 2 I5 in any practical way, so wehave not considered it necessary to show any details of the operativeconnections between the arm 2I I and the switch 2I5. It is enough to saythat the switch contacts 2I5 (Fig. 11a) are normally open so that theconnected signal lamp 2I'I remains unlighted.

When the paper supply has run to a predetermined low point, the arm 2IIis in position 2I Ia and closes the contacts 2 I 6, whereupon the lamp2II lights to inform the attendant that a new roll of paper should beinserted.

Of course, the lamp 2" could be replaced by a buzzer or both kinds ofsignals could be operated by the switch 2 5 5. i

It is very easy to remove an exhausted roll and insert a fresh one onthe core I2'I. All that the attendant has to do is to unhook the brakespring I33a (Fig. 11), lift out the core I21 and push the empty spoolI28 against the circular retaining spring I3I (Fig. 2), which is therebydislodged and rolls down th incline I32 against the shoulder I32. Theempty spool I28 is thus released and a full one slipped over the coreI21.

The attendant now rolls the spring I3I back to its retaining position ingroove I30.

Our machine being of the portable type, we mount a carrying handle 2! onthe top plate I22, which we also use to secure the cover I90 This may bedone in any practical way, as by providing the cover with keys 2Z9 (Fig.1), adapted to be turned in locking engagement with sockets 22!] (Figs.2 and 9) secured to the underside of plate I22. Whenthe cover is inplace, all the mechanism is concealed except the handwheels I16 formeasuring oil a uniform length of recorded sheet and the knife edge I'IIfor tearing it off. The slot I90 of the cover, while above the stylusbelt, is suiiiciently wide to allow the attendant, by looking down atthe machine, to observe the styluses as they record. This visibility ofthe stylus operation enables the attendant to spot instantly any faultyrecording.

Modified platen structure of Figs. 22-25 Figs. 22 to show a somewhatmodified form of platen structure in which the guide strip I59 7 thatconnects the rearwardly flaring extensions I58 in Fig. 4 is replaced bya guide member 22I -mounted above those extensions on the channel barI62. A simple form of guide member 22I consists of a wire bent at theends as shown in r guiding the sheet in its upward movement, as

previously explained for the guide bar I59.

The practical advantage of guide member 22I over the bar I59 is this: Asseen in Fig. 4, the bar I59 is arranged below the stylus path orrecording line 223, so that particles of soot dropping off the styluspoints are liable to accumulate along the top edge of the guide bar andadhere On the other hand, in Fig. 22. where the guide wire 22I isarranged above the stylus path 223, no soot can collect on it and thepaper is left clear.

, In Figs. 22 and 25 we show a single pressure 'roll 224 mounted onshaft I45, in place of the two wheels I44 of Fig. 4, to feed thecontinuous motor driven roller I42. The pressure roll 224 all) providesa continuous contact line across the paper, which is thereby fed evenlyand smoothly into the resiliently mounted platen. When the operatorinserts a new sheet, he pulls the roll 224 forward to position 224 (seeFig. 25), as previously explained for the pressure wheels I44. Whenusing the roll or cylinder 224, we dispense with the guide apron I43 ofFigs. 4 and 9 and substitute a fine coil spring 225, which is stretchedacross the sheet to keep it in smooth condition. The spring 225 has endhooks 226 which pass around the side wings I54 of the platen to hold thespring in place. Finger pieces 22'! make it easy to attach and removethe spring 225.

It is desirable to have the spring 225 as close to the paper as possiblewithout actually touching it. and to obtain this position of the springwe provide the hooks 2 6 with rearwardly curving extensions 226' towhich the ends of the spring are suitably attached, as by solderedjoints 228. It is clear from Fig. 24'that the curved extensions 226'hold the tensioned spring 225 as a straight smooth line in closeproximity to the sheet I34, so that any waves or ripples in the paperare damped out before it reaches the scanning path of the styluses.Otherwise the description of the resiliently mounted platen structure inthe machine of Figs. 1 to 21 applies fully to Figs. 22 to 25.

In the preceding description we have referred to the sheet su portingstructure P as a platen. We use that term broadly both in thespecification and claims to include any practical form of su port forholding the sheet I34 resiliently pressed. against the rigidly mountedstyluses 90. Y The particular machine shownin the drawings was primarilydesigned to operate as a recorder and so we have described it as such.However. we would have it understood that our invention is notrestricted to a facsimile recorder, as it is clearly capable ofembodiment as a transmitter where the copy recorded on sheet I34 isscanned by the styluses in the manner described for the recordingoperation.

It is hardly necessary to add that the various novel features comprisingour invention are capable of practical embodiment in other forms thanherein set forth by way of illustration. b Nor is it necessary toincorporate all of our orig- .inal features in thesame machine, for someof them can be used without others.

We claim as our invention: 4

1. A facsimile scanning mechanism comprising an endless belt, drivingmeans operatively supporting said belt, a plurality of stylus holdersrigidly mounted on said belt in uniform spaced relation, a stylusrigidly carriedby each of said holders, a fixed rail for guiding saidbelt through a scanning path, said rail having a straight rigid 'edgeand means for retaining each of said stylus in steady pressure contactwith said edge throughout its travel through the scanning path. wherebyeach stylus is held in strict alignment .and compelled to move in thesame scanning .path.

2. In a facsimile scanning mechanism, a pair of pulleys, a beltsupported on said pulleys, a plurality of stylus holders carried by saidbelt in .properly spaced relation, means for supporting a stylus by eachof said holders in rigid relation to said belt, a fixed rigid bararranged between said pulleys parallel to said belt and resilient meansfor holding the styluses in pressure con-

